Book IV. 



OPERATIONS OF AGRICULTURE. 



449 



tween paddocks: it consists of bars light at one end (a), and heavy at the other (6), 

 with concealed joints or pivots, in an upright post (c), placed nearer one end of the bars 

 than the other. Then, while the weight of the short ends of the bars keeps them in a 

 fencible position, a slight pressure on the other end will form a passage (rf), which any- 

 one may easily step across. 



2872. Bridges are frequently required on estates and farms for crossing ditches and 

 water-courses. They are generally large stone conduits or barrel-drains ; or in the 

 case of large streams, arches of masonry. In the case of small drains, wooden pipes or 

 boarded tubes are sometimes resorted to, and even earthen pipes have been used ; but 

 masonry should always have the preference. 



2873. The double or folding-gate {^fig. 406.), is considered by some to be much more 

 I durable than 



those of the 

 swing kind ; be- 

 cause the bars, 

 from being only 

 half the length, 

 render the joints 

 ^of the gate not 



so liable to be broken, or the 



hinges to be hurt by straining. 



On the other hand, such gates 



require more time and attention in 



the opening and shutting, and the 



latter operation is troublesome to 



perform, when both halves have 



fallen at the head. These gates are 



not, therefore, in such general use 



in agriculture as the swing kind ; 



but they are common as gates to 



parks, and other scenes of dignity 



and ornament. 



2874. Clarke's window-sash gate 

 (Jig. 407.) is a recent invention, 

 which may be of use in some cases, especially in farm-yards. It is suspended 

 by two weights, and opens and shuts exactly on the principle of the window-sash. 

 The weights may be of stone or cast-iron, and the pulleys are of iron, and nine inches 

 diameter. It was applied in the first instance to a cattle-court ; but has since been 



408 erected in diflerent situations. Its advantages the inventor con - 



siders to be the following: It is easy to open (6), or shut (a) ; 

 remains in whatever situation it is placed ; is not liable to be 

 beat to pieces by the action of the wind ; shuts always perfectly 

 Idose, whatever be the height of the straw or dung in the court 

 ^or gate-way ; a cart may be driven quite close on either side 

 before opening ; is perfectly out of the way when fully open, 

 and not liable to shut on what is passing ; the gate bottom 

 not liable to decay by being immersed in the dung, as is com- 

 monly the case with cattle-court gates ; not liable to go out of 

 order ; may be erected in a hollow place, where a swinging-gate 

 could not open either outwardly or inwardly; and is likely to 

 be more durable than ordinary gates. A small gate of this 

 description (Jig. 408.) is said, by Lasteyrie (Col. de Machines 

 ^c), to have been long in use by the Dutch. 



BOOK V. 



OF THE OPERATIONS OF AGRICULTURE. 



2875. The operations of agriculture are effected under the direction of man, and by 

 means of the mechanical agents, or implements and buildings which we have passed in 

 review in the preceding book. They are either made directly on plants or animals, which 

 may be considered the objects of agriculture ; or on the soil and climate, which are the 

 natural agents of growth and culture. They may be arranged as manual labors and 

 operations, operations with beasts of labor, and mixed operations. 



Gg 



